Field of the Invention
The present invention relates to a method for optimizing an intensity of a useful light distribution.
Description of the Background Art
Traditional beam shaping with optical elements (e.g. diffractive or refractive optical elements) is often effected in a back focal plane of a so-called “1f or 2f construction.” These embodiments are widely used special cases of a general optical construction for generating Fraunhofer diffraction patterns, in which construction e.g. a collimated beam illuminates a beam shaping optical element (e.g. a diffractive optical element) positioned at a distance d upstream of a focusing lens having a focal length f.
The light distribution deflected by the beam shaping optical unit (e.g. by diffraction) is transformed into the desired spatial light distribution to be used (useful light distribution) by means of the focusing lens (having the focal length f) in the back focal plane. For the case of the “2f construction”, reference is generally also made to Fraunhofer diffraction or Fraunhofer observation mode. In these embodiments, the useful light distribution is made available in a plane perpendicular to the optical axis.
The diffraction pattern or the desired light distribution (useful light distribution) in the back focal plane of the lens is also designated as the far field distribution. Disregarding the thickness of the focusing lens, the distance between the beam shaping optical unit and the back focal plane corresponds exactly to the focal length f in the case d=0; exactly to twice the focal length in the case d=f. Therefore, these embodiments are commonly also designated as “1f and 2f construction”. Referring more specifically to the 1f construction (d=0), there is a further special case, which constitutes a fixed combination of beam shaping element and the lens function, the so-called Fresnel element (beam shaping element and lens element are combined as one element).
DE 10 2008 005 219 A1 discloses a device for shaping a light beam which converts a Gaussian profile of the light distribution at the input into a top hat profile at the output, wherein the wavefront of the light beam in the working plane is comparatively flat as a result of profiles of refractive optical elements optimized on the basis of wave equations, as a result of which the desired top hat intensity distribution is present in a larger region around the working plane.
DE 10 2011 119 565 A1 discloses a lighting device which contains diffractive and/or refractive optical elements and converts a Gaussian profile at the input into a top hat profile at the output, wherein an optimization of the light distribution for a target plane inclined relative to the optical axis is effected by optical means.
For certain lighting situations it is necessary and desirable that the useful light distribution is not intended to be made available in a plane perpendicular to the optical axis, but rather in a plane inclined by an angle relative to said plane, wherein the intensity of the useful light distribution is still intended to remain symmetrical and uniform.